Provide method for returning certificate expiration timestamp.

webrtc/base/timeutils.cc

Index: webrtc/base/timeutils.cc
diff --git a/webrtc/base/timeutils.cc b/webrtc/base/timeutils.cc
index fac5b66c7e005756d3c405db60752201ff27602f..05e9ad8243be1eb9447f468bc0fae0955263eed2 100644
--- a/webrtc/base/timeutils.cc
+++ b/webrtc/base/timeutils.cc
@@ -204,4 +204,48 @@ int64_t TimestampWrapAroundHandler::Unwrap(uint32_t ts) {
   return unwrapped_ts;
 }
 
+int64_t TmToSeconds(const std::tm& tm) {
+  static short int mdays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+  static short int cumul_mdays[12] = {0,   31,  59,  90,  120, 151,
+                                      181, 212, 243, 273, 304, 334};
+  int year = tm.tm_year + 1900;
+  int month = tm.tm_mon;
+  int day = tm.tm_mday - 1;  // Make 0-based like the rest.
+  int hour = tm.tm_hour;
+  int min = tm.tm_min;
+  int sec = tm.tm_sec;
+
+  bool expiry_in_leap_year = (year % 4 == 0 &&
+                              (year % 100 != 0 || year % 400 == 0));
+
+  if (year < 1970)
+    return -1;
+  if (month < 0 || month > 11)
+    return -1;
+  if (day < 0 || day >= mdays[month] + (expiry_in_leap_year && month == 2 - 1))
+    return -1;
+  if (hour < 0 || hour > 23)
+    return -1;
+  if (min < 0 || min > 59)
+    return -1;
+  if (sec < 0 || sec > 59)
+    return -1;
+
+  day += cumul_mdays[month];
+
+  // Add number of leap days between 1970 and the expiration year, inclusive.
+  day += ((year / 4 - 1970 / 4) - (year / 100 - 1970 / 100) +
+          (year / 400 - 1970 / 400));
+
+  // We will have added one day too much above if expiration is during a leap
+  // year, and expiration is in January or February.
+  if (expiry_in_leap_year && month <= 2 - 1) // |month| is zero based.
+    day -= 1;
+
+  // Combine all variables into seconds from 1970-01-01 00:00 (except |month|
+  // which was accumulated into |day| above).
+  return (((static_cast<int64_t>
+            (year - 1970) * 365 + day) * 24 + hour) * 60 + min) * 60 + sec;
+}
+
 } // namespace rtc